Conventionally, in a nailer for driving a nail by ae pressure of combustion gas, since an restoring operation due to a spring of a feed piston operated by the combustion gas is performed earlier than an restoring operation of a driver, there may arise a failure of the restoring operation of the driver due to a fact that a next nail is fed to a nose portion and rubs to the driver. Thus, there is proposed a nailer in which a check valve is provided at a former stage of a feeding mechanism so as to hold a gas pressure of the feed piston/cylinder mechanism, and a moving member interlocked with a contact arm performs the sealing control of the tube (for example, a patent document 1).    Patent Document 1: JP-U-05-072380
According to the nailer of JP-U-05-072380, the pressure of the combustion gas supplied to the feed piston is released by the pushing procedure of the contact arm. Thus, in the case where the nailer separates from a member to be driven due to the reaction at the time of the driving operation, the valve is released, whereby the feed piston can not be held and so the feed piston moves to thereby feed a nail to the nose portion. Therefore, there arise problems that a nail rubs to the driver, so that the driver cannot be surely returned and that a nail can not be correctly fed to the nose portion.